Individual golf club heads in a set typically increase progressively in strike face surface area and weight as the clubs progress from the long irons to the short irons. Therefore, the club heads of the long irons have a smaller strike face surface area than the short irons and are typically more difficult for the average golfer to hit consistently well. For conventional club heads, this arises at least in part due to the smaller sweet spot of the corresponding smaller strike face.
To help the average golfer consistently hit the sweet spot on a club head, many golf clubs have heads with so-called cavity back constructions for increased perimeter weighting. Another recent trend has been to increase the overall size of the club heads, especially in the long irons. Each of these features increases the size of the sweet spot and therefore makes it more likely that a ball hit slightly off-center still makes contact with the sweet spot and flies farther and straighter. One challenge for the golf club designer when maximizing the size of the club head is to maintain a desirable and effective overall weight of the golf club. For example, if the club head of a three iron is increased in size and weight, the club may become difficult for the average golfer to swing properly.
In general, the center of gravity (CG) of these clubs is moved toward the bottom and to the back of the club head. This permits an average golfer to get the ball up in the air faster and hit the ball farther. In addition, the moment of inertia (MOI) of the club head is increased to minimize the distance and accuracy penalties associated with hits off-center. In order to move the weight down and back without increasing the overall weight of the club head, material or mass is taken from one area of the club head and moved to another. One solution has been to take material from the face of the club, creating a thin club face. Examples of this type of arrangement can be found in U.S. Pat. Nos. 4,928,972, 5,967,903 and 6,045,456. Thin faces, however, need to be supported to achieve durability and longevity in the club head, and problems associated with the thin faces including vibrations need to be addressed.
A need still exists, however, for improvements in both thin club face support and structural arrangement in golf club heads, and especially for cavity back iron type club heads.